1. Field of the Invention
The invention relates generally to the field of receptor binding assays for analytes in samples suspected of containing the analyte. One problem associated with receptor binding assays for analytes is that samples containing the analytes may contain other materials that will bind receptor reagents utilized in an assay. For example, the interfering material can bind to an antibody which is utilized in the assay, thus reducing the amount of antibody available for binding to an analyte. Another problem is that some analytes bind to interfering materials present in the sample and become complexed. In a complex form the analyte is unavailable for binding to receptors used in the assay and therefore an accurate assay for such analyte is difficult to achieve. Consequently, it becomes necessary to disrupt the binding of the analyte with the interfering material prior to or simultaneously with conducting the assay for the analyte without disrupting binding of the analyte to the receptor.
Urine samples from individuals taking certain non-steroidal, anti-inflammatory drugs such as fenoprofen contain a substance that cross reacts with a subset of the polyclonal antibodies used in testing for drugs of abuse such as antibodies to tetrahydrocannabinol, benzodiazapine, or phenobarbital. The cross-reactive substance or substances are metabolites of fenoprofen that are believed to have little structural resemblance with the analytes to be determined. In order to achieve a more specific assay, it is important that the binding of the cross-reactive antibodies to the interfering metabolites be substantially reduced or eliminated.
Samples to be assayed for the presence of triiodothyronine and tetraiodothyronine also contain thyroxine binding globulin (TBG) which binds to the triiodothyronine or tetraiodothyronine. As a result, quantitation of such analytes in untreated samples is not possible with an immunoassay because a number of molecules of the material free from complexation with TBG will vary with the TBG concentration of the sample. Consequently, it is necessary to disrupt the binding of the triiodothyronine or tetraiodothyronine with TBG prior to or simultaneous with conducting an..assay without interfering with binding of the analyte,with antibody used in the assay. One compound that has been utilized to displace triiodothyronine and tetraiodothyronine from TBG is 8-anilinonaphthalene-l-sulfonic acid.
2. Description of the related art
The use of anilinonaphthalene oulfonic acid for displacing tetraiodothyronine from TBG in assays for tetraiodothyronine is described in U.S. Pat. Nos. 3,928,553 and 3,911,096. European Patent Application 0,133,464 describes the use of 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid and its salts as thyroxine binding protein blocking agents for use in immunoassays and also refers to U.S. patent application Ser. No. 414,934 filed Sep.3, 1982, as disclosing substituted phenylacetic acids.